The invention relates to a method and apparatus for continuously detecting and monitoring the hydrocarbon dew-point or changes in the dew-point properties of a gas.
Presently, there is a need, both onshore and offshore, for a method and apparatus capable of continuously monitoring hydrocarbon dew-point and the amount of condensate produced, at or a little below the dew-point, from pipeline gas.
Dew-point detectors based upon the principle of detecting the presence of dew on a cooled surface, for example a mirror, are already available. Prismatic devices involving visible or infrared light can also be used which rely on the principle of total internal reflection in the absence of a liquid or other medium on the surface. The presence of liquid or other medium on the surface allows light to escape and reduces the intensity of the return beam. Such an imbalance can be used to signal dew-point when condensed liquid forms on the surface and the change in light intensity can be amplified to drive suitable indicating recorders and relays. See, for example, the dew-point detector disclosed in U.S. Pat. No. 3,528,278.
However, in order to obtain an accurate indication of the dew-point it is necessary to meet rigid requirements as to temperature and pressure and it will be necessary to present a gas sample to be investigated under controlled conditions to the detector.